Towards the morphology and biology of the larvae of twosibling-species in the genus Galerucella Crotch (Coleoptera,Chrysomelidae, Galerucinae)

Oxana L. Nesterova1

Abstract. Diagnostic features for larvae of sibling-species Galerucella nymphaeae(L.) and Galerucella aquatica (Geoffr.) are studied. Host plants, distributions onbiotopes and phenology of these species were improved.

Keywords. Galerucella, sibling-species, larvae, morphology, biology.

1. Introduction

The presence of sibling-species among the Chrysomelidae has been well docu-mented (e.g. Berti 1989; Hansen 1994; Nesterova and Lopatin 2002; Lopatin andNesterova 2002). The subject of my research is two sibling-species of the genusGalerucella Crotch: G. nymphaeae (L.) and G. aquatica (Geoffr.). Although usu-ally these species are distinguished by the host plants (Lopatin and Nesterova 2005)and details of imago reproductive structure – aedeagal internal sclerites, diagnosticfeatures of the larvae have not been thoroughly documented (Klausnitzer 1994).The purpose of work was to establish precise features on which it would be possi-ble to distinguish both of a species in their larval stages. In addition, we carriedout research on trophic connections, distributions on biotopes, and phenology ofG. nymphaeae (L.) and G. aquatica (Geoffr.).

2. Methods

The study of the phenology and collecting the samples of the both sibling-specieswere made on one reservoir – pond Pljanta, Nat. Park Belovezhskaja pushja, Bela-rus, in 2005 (Fig. 1). Larvae were fixed with 70% ethanol, processed in glycerin onglass. Observations were made with microscope Zeizz Stemi 2000. The study of thehistory of these species were made in laboratory boxes.

1 Department of Zoology, Byelorussian State University, Independence ave. 4, 220030

Minsk, Belarus. oxana@list.ru

3. Results

3.1. Biology

Both of species are hygropholius, their life cycle is connected with reservoirs andthey can live sympatricontemporaneously. The phenology of these two sibling-spe-cies is similar (Table 1): bivoltine with the imago present during the winter. Imagoand larvae of Gallerucella nymphaeae feeds on leaves of Nuphar lutea (L.) Smith.floating on the water, live in the zone of contact between the plant and the water.Larvae and pupae can sometimes be on the bottom part of a leaf and be completelyimmersed in water. Conversely, G. aquatica feeds on coastal vegetation of reser-voirs, on bogs, on marshy coast of the rivers. In general, G. aquatica does notcontact the water.

Gallerucella nymphaeae feeds on the plants of the Nymphaeaceae Salisb.(Nymphaeae L. and Nuphar Smith.); the host plants of G. aquatica belong in thePolygonaceae Juss. (Rumex L., in the nature, R. hydrolapathum Huds., in laboratoryboxes larvae completed their the history also on R. acetosa L., R. acetosella L.,R. crispus L. and R. confertus Willd.).

Interspecific competition between these sibling-species of Galerucella is reducedowing to their differences in habitats and use of different food resources.

The larvae of two sibling-species in the genus Galerucella Crotch 115

Figure 1. The habitats of Galerucella aquatica and Galerucella nymphaeae (pond Pljanta).

The morphological differences in the larvae (first and final instars) of these sibling-species have allowed finding precise differences between species leading to bettercircumscription of the taxa.

3.2. Systematic Entomology

Galerucella aquatica (Geoffr.)Plates 5 and 6; figs. 2-11.

Material Examined: 13.07.2005, Belarus, pond Pljanta, Nat. Park Belovezhskajapushja, on Rumex hydrolapathum.

Final instar larva (Plates 5 and 6). Body straight, cylindrical, flexible, 7.5-9 mm long,light-amber in color, with dark-brown sclerites and head capsule. Head (Figs. 2 and3) 0,7-0,8 mm in width, hypognathous, roundish, shiny, with one pair of light,strongly convex ocelli. Epicranium convex, with five pairs of macrosetae and threepairs of microsetae (one pair located near frontal sutures and two pairs near ocelli).

116 Oxana L. Nesterova

Galerucella aquatica Galerucella nymphaeae

Body length 7,5-9 mm 9,5-10,mm

Head capsule suboval round

Frons with 4 pairs of macrosetae with 3 pairs of macrosetae

Clypeus with 3 pairs of microsetae with 2 pairs of microsetae

Labrum with 4 pairs of marginal microsetae with 3 pairs of marginal microsetae

Mandibles with blunt, short teeth; fourthtooth is very narrow, tooth onmolar margin is smoothed

with acute, long teeth; fourthtooth is wider, tooth on molarmargin is distinct

Stipes with 3 macrosetae with 2 macrosetae

Palpiger with 2 macrosetae with 1 macroseta

Setae on body terga longer shorter

Sclerites on terga located tightly, but spaced betweensclerites are distinct

located more tightly, spaces arehardly visible

Length of thorax terga pronotum insignificantly longerthan others thorax terga, propor-tions of segment as 9 : 8 : 7

pronotum longer than others tho-rax terga, proportions of segmentas 17 : 14 : 13

Prescutal sclerites ofmeso- and metathorax

independent fused

Sternal sclerites ofmeso- and metathorax

entire, with 2 setae divided on 2 sclerites, with one setaon each

Sternal sclerites of nine-teenth adominal segment

entire, with 4 setae divided on 2 sclerites, with 2 setaon each

Lobe of pygidium closed pulled out

Table 1. Differences of the final instar larvae of sibling-species G. aquatica and G. nymphaeae.

Epicranial suture long, frontal sutures slightly marked. Frontal plate with narrowtriangular apex and convex anterior margin, with two pairs of depressions in centreand four pairs of macrosetae.

The larvae of two sibling-species in the genus Galerucella Crotch 117

Figures 2–11. Galerucella aquatica. Figs. 2–9: Final instar larva. 2. head, frontal view; 3. head, lateralview; 4. labrum; 5. mandible; 6. maxillolabial complex; 7. thoracic segments and first abdomi-nal segment (D-D and V-V – middle lines of dorsal and ventral sides); 8. ninth abdominal seg-ment and pygidium (ventral view); 9. leg. Figs. 10–11: First instar larva. 10. head, frontal view;11. mandible.

2 3

10

4

5

11

6

89

7

Antennae two-segmented: basal segment cylindrical, with one microseta and largeconical sensorium, apical segment in twice smaller than sensorium. Clypeus withthree pairs of microsetae, located on its infuscated upper half.

Labrum (Fig. 4) with long triangular apex and strait cutting anterior margin,with four discal macrosetae and eight marginal microsetae. Upper part of labruminfuscated, strongly sclerotized, lower one almost transparent. Mandibles (Fig. 5)triangular, wide, with four apical teeth: three teeth short, wide and blunt, fourthtooth turned on inner side of mandibles, shorter than others and very narrow.Molar margin of mandibles with feeble smooth tooth and thin, unsclerotized pro-cess. Outer surface of mandible with one macroseta.

Maxillolabial complex (Fig. 6) moderately sclerotized. Submenthum and men-thum with hardly visible border, with two pairs of macrosetae; prementhum wellseparated from menthum, darker and strongly sclerotized, with two microsetae onouter margin and two-segmented labial palpi. Cardo large, without setae; stipeswith three macrosetae. Palpiger not large, with two macrosetae; galea and laciniafused in base, with wisp of short robust setae on apex. Maxillar palpi two-seg-mented: basal segment cylindrical, with one seta apical, one conical.

Body covered with dark setae. Sclerites large, located closely, but light spaces be-tween sclerites clearly visible.Thorax and abdomen (Fig. 7). Tergum of pronotum insignificantly longer thanterga of mesonotum and metanotum, proportions of notum segments as: 9 : 8 : 7.Wide central sclerite divided by light longitudinal central strip, with six macro-setae on each half, located on margins. Epipleural sclerites of pronotum very large,with two macrosetae. Trochantin of thorax segments with one seta. Prothoracicspiracle situated in mesothorax region. Sternal sclerite of prothorax quadrangular,with four macrosetae. Prescutal sclerites of mesonotum and metanotum pulled to-gether, but border between these sclerites visible. Inner and outer prescutal andscutellar sclerites of mesonotum and metanotum with one seta. Dorsolateral scler-ites with three macrosetae. Epipleural and pleural sclerites with one seta. Sternalsclerites of meso- and metanotum reduced in twice and with two microsetae; pairof microsetae located below sternal sclerite.

Coalesced prescutal and coalesced scutellar sclerites of abdominal terga resem-ble two transversal sclerites with two setae on each. Dorsolateral abdominal scler-ites with one seta. Epipleural sclerites have two macrosetae. Pleural sclerite withone seta. Parasternal and sternal sclerites with two microsetae. Spiracles round,dark, located on convex stigmal plates.

Nineteenth segment of abdomen covers pygidium (Fig. 8), with four setae onsternite and ten macrosetae, located in one row on distal margin of tergum. Pygi-dium light, soft, two-lobed; lobes cylindrical, closed.

Legs (Fig. 9) well-developed. Coxa with three setae, trochanter without sharpcontour, darked. Femur with three setae on inner surface and four setae aroundapex. Tibia-tarsus with two groups of setae: four setae located around before apical

118 Oxana L. Nesterova

1/3 of tibia-tarsus and five setae located around apex. Claws not large, acute, curved.Chelonium large and light.

First instar larva (Figs. 10 and 11). Body 0,8-1,3 mm in length. It differs fromolder instars in morphology of mandibles (Fig. 11): apical teeth narrow, long andacute, molar margin with well-developed tooth and long unsclerotized process. Be-sides, frons almost flat, its depressions not deep.

Galerucella nymphaeae (L.)Plates 7 and 8; figs. 12-21.

Material Examined: 13.07.2005, Belarus, pond Pljanta, Nat. Park Belovezhskajapushja, on Nuphar lutea.

Final instar larva (Plates 7 and 8). Body light-brown or amber, 9,5-10,5 mm inlength, sclerites and head capsule black-brown in color. Head (Figs. 12 and 13) 1,3-1,4 mm in width, hypognathous, round, shiny, with one pair of light, convex ocelli.Epicranial suture long, frontal sutures distinct. Epicranium convex, with two pairsof macrosetae and one pairs of microsetae, located along frontal sutures, two pairsof microsetae located near ocelli and two macrosetae near antennae. Frons de-pressed in the middle, with six macrosetae and convex anterior margin.

Antennae two-segmented: basal segment large, cylindrical, with one microsetaand large sensorium, apical segment conical and shorter than sensorium.

Clypeus with four microsetae and infuscated upper margin. Labrum (Fig. 14)with triangular apex and roundish appearing anterior margin, with four discalmacrosetae and six marginal microsetae.

Mandibles (Fig. 15) triangular, with four long, acute apical teeth and one macro-seta on outer surface. Molar margin of mandibles with small, distinct tooth andvery short, thin unsclerotized process.

Maxillolabial complex – figs. 16. Submenthum and menthum fused, with fourmacrosetae. Prementhum with distinct border and two microsetae. Labial palpitwo-segmented. Ligula with group of fine short setae. Cardo suboval, with dark tri-angular spot and without setae. Stipes with two macrosetae, palpiger with onemacroseta. Maxillar palpus two-segmented: basal segment cylindrical, with oneseta, apical segment conical. Galea fused with lacinia in base, with numerous hardsetae on apex.

Body with dark, short setae; sclerites large, located very tightly.Pronothum and abdomen – fig. 17. Tergum of pronotum longer than terga of

others segments of thorax, proportions of notum segments as 17 : 14 : 13. Centralsclerite of pronotum divided by light longirudinal central strip, has four macro-setae and four microsetae. Epipleural sclerites of pronotum convex, with two macro-setae. Trochantin and pleural sclerites of thorax have one seta. Spiracle of protoraxmoved posteriad. Sternal sclerites of prothorax with four setae. Prescutal scleritesof mesonotum and metanotum tightly pulled together and space between sclerites

The larvae of two sibling-species in the genus Galerucella Crotch 119

hardly visible. Scutellar sclerites of mesonotum and metanotum fused, with one totwo microsetae.

Dorsolateral sclerites with three setae. Epipleural sclerites and trochantin withone seta.

120 Oxana L. Nesterova

Figures 12–21. Galerucella nymphaeae. Figs. 12–19. Final instar larva. 12. head, frontal view; 13. head,lateral view; 14. labrum; 15. mandible; 16. maxillolabial complex; 17. thoracic segments and firstabdominal segment (D-D and V-V – middle lines of dorsal and ventral sides); 18. ninth ab-dominal segment and pygidium (ventral view); 19. leg. Figs. 20–21. First instar larva. 20. head,frontal view; 21. mandible.

12 13

1415

16 17

18

19

20

21

Sternal sclerites of mesothorax and metathorax diminish to two small sclerites withone microseta on each, one microseta located between these sclerites and one pairof microsetae located below sclerites.

Prescutal and scutellar sclerites of abdomen fused into two transverse elongatedsclerites. Scutellar sclerites have two microsetae. Dorsolateral sclerites with onemicroseta. Spiracles round, dark, located on convex stigmal plates. Pleural tuberclewith small, but well-developed sclerites, bearing one microseta.

Parasternal sclerites diminish to two small plates with one seta on each. Sternalsclerites with pair of setae.

Tergum of nineteenth abdominal segment (Fig. 18) with row of 10 macrosetae,sternal sclerites with four setae. Two cylindrical lobes of pygidium widely pulledout.

Legs (Fig. 19) not long. Coxa with two microsetae, trochanter fused with femur;femur has five to six setae. Tibia-tarsus with three pairs of setae, located on tworounds on apex. Claws acute, curved, with one seta on base. Chelonium large, light.

First instar larva (Figs. 20 and 21). Body 1,5-1,8 mm long. Morphology of mouth-parts and head capsule of different instars larvae similar with the exception form ofmandibles of youngest larva: fourth tooth very narrow and hardly visible, turnedon inner side of mandibles.

References

Berti, N. 1989. Contribution a la Faune de France. L’identite d’Oulema (O.) melanopus (L.) (Col.Chrysomelidae, Criocerinae). Bulletin de la Société entomologique de France 94: 45-47.

Hansen, M. 1994. Bladbillen Oulema melanopus (Linnaeus, 1758) et kompleks af to arter (Coleoptera,Chrysomelidae). Entomologiske Meddelelser, Copenhagen 62: 27-30.

Nesterova, O.L. & Lopatin, I.K. 2002. Sibling-species in leaf beetles fauna (Coleoptera, Chrysomelidae)of Eastern Europe and northern Asia. Bulletin of Belarus State University, Series 2, No 2: 39-42.

Lopatin, I.K. & Nesterova, O.L. 2002. Review of species of genus Cryptocephalus Geoffr. of groupflavipes F. (Coleoptera, Chrysomelidae). Euroasian Entomological Journal 1(2): 215-217.

Lopatin, I.K. & Nesterova, O.L. 2005. Insecta of Belarus: Leaf-beetles (Coleoptera, Chrysomelidae):294 pp. uu ‘Technoprint’, Minsk.

Klausnitzer, B. 1994. Die Larven der Käfer Mitteleuropas Band 2, Teil 1: pp. 283-288. Goecke & EversVerlag, Krefeld.

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